Atmospheric correction for inland waters—application to SeaWiFS

Abstract

Inland waters are an increasingly valuable natural resource that has major impact and benefits for population and environment. The new generation of ocean colour sensors has better spatial resolution, and hence are suitable for monitoring water quality of lakes. As an alternative to standard algorithms developed for oceans, which often fail over inland waters, we propose here a scheme based on aerosol remote sensing over land. The ocean colour sensors have spectral bands that allow characterization of aerosols over dark land pixels (vegetation in the blue and in the red spectral bands). It is then possible to use a representative aerosol model (aerosol optical thickness and aerosol type) for atmospheric correction over inland waters after validating the spatial homogeneity of the aerosol model in the lake vicinity. The performance of this new algorithm is shown in Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) scenes of Lakes Balaton (Hungary) and Constance (Germany). We demonstrate the good spatial homogeneity of the aerosols and the meaningfulness of the water‐leaving reflectances derived over these two lakes.

We also addressed the particularity of Fresnel reflection computation. The direct to diffuse term of this Fresnel contribution is reduced because of the limited size of the lake. Based on the primary scattering approximation, we propose a simple formulation of this component. A specific Fresnel correction needs to be developed to fulfil the accuracy requirements.

Acknowledgements

The authors would like to thank to DAAC at the GSFC for the production and the distribution of the level 1a SeaWiFS images. This work was supported by the European Community in the Fifth Framework Program, IST, in the SISCAL project